Manufacture of polyurethanes using organic zirconium compounds as catalysts

ABSTRACT

In the manufacture of a polyurethane by the reaction of a polyol with a polyisocyanate in the presence of a catalyst and in the absence of water, the catalyst used is an organic zirconium compound, preferably a zirconium alcoholate or phenolate, having the formula: (Y)mZr(YR)4 2m WHEREIN: Zr is a zirconium atom Y is an oxygen or sulfur atom R is an organic radical of up to 12 carbon atoms, which can be alike or different M IS 0 OR 1.

United States Patent Dijkhuizen et al.

[ June 27, 1972 [54] MANUFACTURE OF POLYURETHANES USING ORGANICZIRCONIUM COMPOUNDS AS CATALYSTS many [ 73] Assignee: Dynamit NobelAktiengesellschaft,

. Troisdorf, Germany I22] Filed: May ll. I970 [21] Appl. No.: 48,775

[30] Foreign Application Priority Data May 10, 1969 Germany... ..P 19 23934.0

[52] US. Cl. ..260/77.5 AB, 260/25 AB, 260/75 NB [5 l Int. Cl ..C08g22/40 [58] Field of Search ..260/77.5 AB, 75 NB, 2.5 AB

[56] References Cited UNITED STATES PATENTS 3,136,731, 6/1964 Piechotaet al. ..260/77.5

OTHER PUBLICATIONS Britain et al., J. Applied Polymer Sci., 4, No. l 1,pp. 207- 21 1, l960.

Primary ExaminerDonald E. Czaja Assistant ExaminerM. J. WelshAttorney-Burgess, Dinklage & Sprung [57] ABSTRACT In the manufacture ofa polyurethane by the reaction of a polyol with a polyisocyanate in thepresence ofa catalyst and in the absence of water, the catalyst used isan organic zirconium compound, preferably a zirconium alcoholate orphenolate, having the formula (Y)mZr(YR)4 zm 7 Claims, No DrawingsMANUFACTURE OF POLYURETHANES USING ORGANIC ZIRCONIUM COMPOUNDS ASCATALYSTS PRIOR ART Polyurethanes are made by the reaction of polyolswith polyisocyanates according to the isocyanate polyaddition process.Suitable polyols are: polyethers, polythioethers, polyesters, polyesteramides and polyacetals. The polyisocyanates can be any of most of thetypes known today, preferably diand triisocyanates. Either the so-calledoneshot" process or the prepolymer process can be used for the additionpolymerization.

The reaction of the isocyanate groups with the active hydrogen atoms ofthe polyols is usually accelerated by means of catalysts. It has longbeen known that tertiary amines have an accelerating action of thiskind. In addition to the tertiary amines, organic metal compounds, suchas tin(ll) octoate and di-n-butyl tin dilaurate, can be used ascatalysts. Organic metal compounds which, in an addition to an alcoholicbinding of the metal to the organic moieties, also contain aco-ordinative bond are particularly good catalysts. Such chelatecompounds are, for example, the acetyl acetonates of zirconium, vanadiumand titanium.

All of the catalysts of the prior art, however, have disadvantages. Forexample, in many catalysts the accelerating action is insufficient.Acetyl acetonates are not soluble or are insufficiently soluble in manyreaction systems, so that they have little catalytic effect.

It is also known that, in the manufacture of polyesterpolyisocyanatefoams, wherein water is used as the foam forming agent and a tertiaryamine is used as the accelerator, the pore structure of the foam can beadvantageously affected by the addition of zirconium alcoholates derivedfrom longchained alcohols having at least six carbon atoms.

REFERENCES Kunststoffhandbuch, Vol. VII,

Hanser-Verlag 1966. e

THIS INVENTION It has now been found that, in certain reaction mixturesfor the synthesis of polyurethanes, which are substantially free ofwater, and in which most acetyl acetonates do not dissolve, the additionof zirconium or zirconyl alcoholates or phenolates produces a favorablecatalytic action on the polymerization reaction.

In addition to this favorable catalytic action, an additional technicaladvantage has been surprisingly found. If such systems contain traces ofwater, these traces can very easily be removed by the addition of thezirconium alcoholates. That is, these alcoholates react with water toform the corresponding polymeric esters having about four to sixzirconium atoms in the molecule, and also to form, in part, thecorresponding alcohols and zirconium hydroxy compounds which in turn arecapable of entering into reactions with isocyanate groups. It isrecommended that the zirconium alcoholates be added to the componentcontaining traces of water in a preliminary stage, to first dehydratethis component before the isocyanate is added.

The process of this invention for the manufacture of unfoamedpolyurethanes comprises the reaction of polyisocyanates with polyols bythe addition polymerization process in the presence of a zirconiumcompound catalyst and/or water-binding agent, which compound has theformula:

)m )42m wherein Y represents oxygen or sulfur, m l or 0, preferably 0,and R has preferably up to 12 carbon atoms and represents in each casean identical moiety or a plurality of different preferably a branched orunbranched alkyl moiety having one to five carbon atoms, and having insome cases an oxygen or sulfur atom between two carbon atoms, thesecompounds being soluble in the reaction mixture. In some cases, they areprepared by condensation wholly or partially with the intermolecular orintramolecular loss of alcohol or thioalcohol, or phenol or thiophenol,as the case may be. The polyols used in the process are preferablysubstantially anhydrous.

THE CONVENTIONAL REACT ANTS The polyols used are preferably polyetherpolyols having a functionality in regard to isocyanate groups of 2 to 9and hydroxyl numbers of 30 to 600. Such polyether polyols can beprepared by the reaction of polyvalent alcohols with alkylene oxides.Glycerine, trimethylol propane, pentaerythritol, sorbitol, glucose andsaccharose can be used, for example, as polyvalent alcohols. Examples ofsuitable alkylene oxides are propylene oxide, 1,2- 1,3- and2,3-epoxybutane, styrene oxide and epichlorhydrin. Also mixtures ofthese substances with up to 30 percent by weight of ethylene oxide areuseful. The reaction can be catalyzed by bases. Preferably, however,polyether polyols are used which have been obtained by a reaction ofthis kind with acid catalysis, using boron trifluoride, for example. Itis characteristic of such polyether polyols that, in addition tosecondary hydroxyl groups, they contain a considerable amount of primaryhydroxyl groups.

One preferred manufacturing process is described, in British Pat. No.1,016,689. In all of these saccharide-base polyols used. according tothe invention, it is possible, of course, in the final analysis, tostart with starch which can easily be transformed by prior-art methodsinto the monosaccharides or oligosaccharides.

Also usable as polyols in the meaning of the invention are polyethers ofethylene diamine and/or diethylene triamine-alkylene oxides orpolyesters, e.g., those of adipic acid and ethylene glycol, which haveterminal hydroxyl groups.

Lastly, polyethers such as can be obtained, for example, by thepolyaddition of epoxy compounds and water can also be used according tothe invention. Polyethylene oxide, polypropylene oxide,poly-l,2-butylene oxide and polyepichlorhydrin are examples.Polybutylene oxide can also be obtained by the polymerization oftetrahydrofuran.

In the polyols obtained according to British Pat. No. 1,016,589 andother polyether polyols, most acetyl acetonates and chelates areinsoluble or insufficiently soluble, while the zirconium-containingcatalysts used according to the invention are readily soluble therein.

All of the isocyanates used today in the polyurethane art are usable asthe polyisocyanates in this invention. diand triisocyanates are alsopreferred, such as aliphatic and aromatic isocyanates having a valenceof two and more, e.g. alkylene diisocyanates like tetraand hexamethylenediisocyanate, arylene diisocyanates and corresponding alkylationproducts such as mand p-phenylene diisocyanate, naphthylenediisocyanate, diphenylmethane diisocyanate, toluylene diisocyanates suchas 2,4- and 2,6-toluylene diisocyanate and their mixtures, diandtriisopropylbenzene diisocyanate and tn'phenylmethane triiso-cyanate,p-isocyanatophenylthiophosphoric acid triester,p-isocyanatophenylphosphoric acid triester, aralkyldiisocyanates such asl-(isocyanatophenyl)-ethylisocyanate or m-and p-xylylenediisocyanate, aswell as polyisocyanates of the types enumerated above which aresubstituted by various groups, such as alkyoxy-, aryloxy-, N0 and Cl.Also, polyphenylpolymethylenepoly-isocyanate obtained by thecondensation of aniline and formaldehyde followed by phosgenation; andthe products of the reaction of the abovementioned isocyanates with aninsufficiency of polyhydroxyl compounds, such as, for example,trimethylolpropane, hexanetriol, glycerin and butanediol.Polyisocyanates masked by phenols or bisulfite, and polymerizedisocyanates having an isoryanurate ring structure can also be used.

PROCESSING CONSIDERATIONS isocyanate groups withj'the water. Adehydrating agent, such,

as zeolite, hasoften been usedfor this purpose. Now, it has been foundthatthe zirconium compounds used according to the invention are alsocapable of removing the water from the polyol. For this purpose thepolyol that is to be used for the process of the invention is mixed withthe amount of the zirconium compound that is equivalent to the watercontained in the polyol and left standing for a period of time at roomtemperature.

Theisocyanateis then stirred'in and the reaction mixture thus producedis poured into a mold where the addition polymerization is completed.Generally the casting can be stripped from the mold after a briefperiod. With this procedures stable material is obtained without bubblesor foam.

Basically, cross-linking agents of the prior art can also be used, suchas glycol, butanediol, ethylenediamine, 1,3- diaminopropane, 4,4-diaminodiphenylemethane and hydrazine. In that case either the one-shotprocess or the preopolymer" process of the'prior art is employed. Inthisprocedure it is often necessary to modify the quantity ratios of thereactants, but it is easy to determine these ratios by preliminaryexperiments. Generally speaking, an excess of the isocyanate and aninsufficiency of the cross linking agent will be used, with respect tothe polyol.

THE NEW CATALYST The catalyst used according to this invention arezirconium alcoholates or phenolates, zirconyl alcoholates or phenolateswhich contain tetravalent zirconium, and the corresponding zirconiumcompounds in which the oxygen atoms attached to the zirconium' atom arewholly or partially replaced by sulfur atoms. These zirconium compoundsare derived from primary, secondary or tertiary aliphatic alcohols ortrialcohols with up to five carbon atoms, which can contain oxygen orsulfur bridges in the aliphatic hydrocarbon moieties. Also suitable arezirconium compounds which-derive from cycloaliphatic alcohols or fromarylalkyl alcohols, and the analogous thioalcohols. Furthermore, those.zirconium compounds are also usable accordingto this invention ascatalysts, which derive from phenols or thiophenols containing, ifdesired, alkyl groups on the aromatic ring, or from a number ofdifferent compounds, e.g., from aliphatic and aromatic compounds,containing hydroxyl groups.

Lastly, the condensation products of the above-enumerated zirconiumcompounds, such as are formed by the loss of alcohol orthioalcohol, orphenol or thiophenol as the case may be, can be used as catalysts.Preference is given to the use of those condensation products whichcorrespond to the general formula Zr( YR ),-(Y--Zr( YR),),,Y Zr( YR)=,,wherein Y and R have the meaning stated previously, and wherein n is anumber between 0.2 and 10.

In detail, the following substances, among others, are suitable:zirconium tetra-n-propylate, zirconium tetraisobutylate, zirconiumtetracyclopentylate, zirconium tetraethylglycolate, zirconiumtetra-n-thiopropylate, zirconium tetraphenolate, zirconiumtetrathiophenolate, zirconyl diethylate, zirconyl dithiopropylate. It isan essential requirement the catalysts be soluble in the reactionmixture. The use of zirconium acetylacetonate or, generally, of chelatesof zirconium does not come within the scope of this invention- IADVANTAGES An advantage of this type of catalyst is that thepolyaddition takes place completely so that polyurethanes are obtainedwhich are characterized by outstanding mechanical and electricalproperties. The mechanical properties are especially apparent in thepreparation. of glass fiber reinforced polyurethanes, where the windingprocess is used, and in the use of polyurethanes as binding agents forporphyry corundum in'the making of wear-resistant surfaces in roadconstruction. In the latter case; the rapid setting action is of greatimportance.

If the process according to the invention is used in casting, it hasbeen found that the dissipation of the heat of reaction is very good,even in thick-walled castings. Materials are obtained which arehomogeneous and free of streaks. This'also contributes towardsgoodmechanical characteristics, such ashigh breaking strength andtensile strength. Particularly outstanding is the modulus of elasticityand the impact toughness.

With regard to the desirable dehydration effect which the zirconiumcompounds have on the starting substances, particularly the polyols, asdescribed above, it is also to be stressed that a smaller amount of thezirconium compound needs to be used than in the case of otherdehydrating agents, such as zeolite, in order to achieve the sameeffect. There is virtually no encumbering of the reaction mixture byoften undesirable powered solids. Re-cleavage of the water at hightemperature as in the case of zeolite is impossible.

In the manufacture of sheet materials or films by the present processanother advantage is obtained. Polyurethane-base sheet materials usuallyhave an irregular and bubbly surface. This is not always to beattributed to moisture in the starting products for the polyurethane,but often is also due to the humidity of the ambient air. The waterreacts with isocyanate groups in the surface layers of the reactionmixture, and this undesired reaction is commonly known to result in theevolution of CO and the formation of bubbles. In the process of theinvention, the presence of the zirconium compounds leadsto anacceleration of the reaction between the isocyanate and the polyhydroxylcompound as well as cross-linking agent, if any, to such an extent thatthe atmospheric moisture cannot compete. Bubble formation is preventedsince the zirconium compounds eliminate even the last traces of waterfrom the reaction compositions. Surprisingly, the sheets and films havea uniform, smooth surface. It is also to be noted that the stickiness ofthe surface vanishes in a very short time.

EXAMPLES EXAMPLE l The polyol in the experiments was a liquid productbased on glucose and propylene oxide such as can be prepared by acidcatalysis according to Example 2 of British Pat. No. 1,016,589. It hadan OH number of 269 and contained about 0.2 weight percent water. 181.5g of this homogeneous, liquid product was placed in a sealed vessel, 4.5g of zirconium tetran-propylate was added to bind the water, and themixture was let stand overnight. On the next day, under intenseagitation, I 18.6 g of a liquid, solvent-free polyisocyanate mixturecontaining diphenylmethane-4,4' -diisocyanate as the principal componentwith an effective content of 92 mole-percent, was poured into thevessel. The addition polymerization started immediately, with theevolution of heat. The mixture was immediately poured into test-specimen.molds, 10 X 15 X mm. The compound had hardened by 12 minutes after thead dition of the isocyanate. The test specimens were stripped out 60minutes after casting and heated in a drying oven for 3 hours at 1 10 C.

The cast polyurethane resin prepared in this manner was completely freeof bubbles. On the following day the bending test per DIN 53,452 and theimpact bending test per DIN 53,453 were performed. The following valueswere obtained (average of 5 individual measurements): Bending strength900 COMPARATIVE TEST In a second batch, dibutyl tin dilaurate was usedas the catalyst instead of zirconium tetra-n-propylate. Also, the polyolwas dehydrated by means of zeolite.

In detail, the following procedure was used. 240 g of the polyolmentioned above was placed in a half-liter stirrer vessel and 24 g of adispersion of 50 percent zeolite by weight in castor oil was added. Thenthe mixture was heated with stirring to 100 C., and at the same time thepressure in the reactor was lowered to about mm Hg. These reactionconditions were sustained for 3 hours. Then the mixture was cooled to 25C., and the pressure was then raised to normal. 181.5 g of the polyolthus dehydrated was placed in the reaction vessel and 0.2 g of dibutyltin dilaurate was added. Otherwise, the operations were the same asdescribed above. In this second batch the setting time was againapproximately 12 minutes. The cast test specimens were tested accordingto the same DIN standards.

The results were as follows: bending strength: 730 kg/cm" modulus ofelasticity: 24,760 kg/cm" impact toughness: 19.9 kp cmlcm EXAMPLES 2 to8 In the following experiments, the polyol was also a liquid productderived from glucosepropylene oxide such as can be prepared by acidcatalysis according to British Patent No. 1,016,589. It had a hydroxynumber of 314. In each case the polyol was dehydrated with zeolite byprocedures similar to the one described in connection with thecomparative experiment in Example 1. Further processing to thepolyurethane was performed by the procedure outlined in Example 1,except that, instead of zirconium tetra-n-propylate, different catalystswere used in different quantities. The last experiment was performedwithout the use of a catalyst.

The table lists the setting times and temperatures in relation to theamount of catalyst used. From these figures it is apparent that thezirconium compounds according to the invention do accelerate theaddition polymerization.

TABLE Catalyst Ex. Quant. as Set- Set- Type of wt. ting ting of the timetemp.

polyol min. C

2 Zirconium-n-propylate 0.35 l 0 87 3 Zirconium-n-propylate 0.14 28 70 4Zirconium-n-propylate 0.08 60 44 5 Zirconium-n-butylate 0.35 16 66 6Zirconium-n-butylate 0. l 4 61 41 7 Zirconium isobutylate 0.35 60 8 Nocatalyst l 3 7 30 We claim:

1. In the manufacture of a polyurethane by the reaction of asubstantially anhydrous polyol with a polyisocyanate in the presence ofa catalyst, the improvement comprising using as said catalyst an organiczirconium compound soluble in the reaction mixture and having theformula Zr is a zirconium atom,

Y is an oxygen or sulfur atom,

R is an organic radical having upto 12 carbon atoms and is selected fromthe group consisting of cycloalkyl, arylalkyl, alkylaryl, aryl or alkyl,the alkyl radicals of which can be branched or contain oxygen or sulfuratoms, in the chain,

m is 0 or I, and

n is 0.2 to 10.

2. The process of claim 1 wherein said polyol is a poly-ether polyolhaving a functionality in relation to isocyanate groups of 2 to 9 and ahydroxyl number of 30-to 600 and said catalyst is present in an amountin the range of 0.01 to 5 weight percent, based on said polyol.

3. The process of claim 1 wherein said catalyst has the formula:

4. The process of claim 1 wherein R is an alkyl group having in therange of one to five carbon atoms.

5. The process of claim 4 wherein said catalyst is selected from thegroup consisting of zirconium tetra-n-propylate, zirconium-n-butylate,and zirconium tetra isobutylate.

6. The process of claim 1 wherein at least a portion of said catalyst isadmixed with said polyol prior to the addition of said polyisocyanate,to assure the dehydration of said polyol.

7. The process of claim 6 wherein said polyol has an initial watercontent greater than 0.08 weight percent and said catalyst is admixedtherewith and the mixture allowed to stand for some time at roomtemperature.

2. The process of claim 1 wherein said polyol is a poly-ether polyolhaving a functionality in relation to isocyanate groups of 2 to 9 and ahydroxyl number of 30 to 600 and said catalyst is present in an amountin the range of 0.01 to 5 weight percent, based on said polyol.
 3. Theprocess of claim 1 wherein said catalyst has the formula: Zr (YR)3-(Y-Zr(YR)2)n-Y-Zr (YR)3.
 4. The process of claim 1 wherein R is an alkylgroup having in the range of one to five carbon atoms.
 5. The process ofclaim 4 wherein said catalyst is selected from the group consisting ofzirconium tetra-n-propylate, zirconium-n-butylate, and zirconium tetraisobutylate.
 6. The process of claim 1 wherein at least a portion ofsaid catalyst is admixed with said polyol prior to the addition of saidpolyisocyanate, to assure the dehydration of said polyol.
 7. The processof claim 6 wherein said polyol has an initial water content greater than0.08 weight percent and said catalyst is admixed therewith and themixture allowed to stand for some time at room temperature.